Guest-host mode liquid crystal display device of lateral electric field driving type

Abstract

A liquid crystal display device comprising a light modulating layer being interposed between a first substrate and a second substrate, a common electrode being formed over the first substrate in parallel with a drain electrode, wherein an electric field is formed between the drain electrode and the common electrode in a parallel direction to the first substrate, wherein said light modulating layer comprising a liquid crystal material, an optically active substance and a dichroic dye is operated in a guest-host mode, wherein said liquid crystal material has a spiral pitch p in a range of 1<p<15 μm, and wherein a cell thickness d is in a range of 1<d<10 μm.

What is claimed is:  
     
       1. A liquid crystal display device comprising: 
       a first substrate;  
       a second substrate opposing to the first substrate;  
       a light modulating layer being interposed between the first substrate and the second substrate;  
       at least a pixel being formed over the first substrate, said pixel comprising:  
       a thin film transistor including a source region, a drain region, a channel region being interposed between the source and drain regions, a gate electrode being adjacent to the channel region with a gate insulating film interposed therebetween;  
       a drain electrode being connected to the drain region;  
       a gate line being connected to the gate electrode;  
       a common electrode being formed in parallel with the drain electrode;  
       a common line being connected to the common electrode,  
       wherein an electric field is formed between the drain electrode and the common electrode in a parallel direction to the first substrate,  
       wherein said light modulating layer is operated in a guest-host mode,  
       wherein said liquid crystal display device includes no polarizing plate,  
       wherein said light modulating layer comprises a liquid crystal material, an optically active substance and a dichroic dye,  
       wherein said liquid crystal material has a spiral pitch p in a range of 1≦p≦15 μm, and  
       wherein a cell thickness d is in a range of 1≦d≦10 μm.  
     
     
       2. A device according to  claim 1 , wherein the source region, the drain region and the channel region are formed in a crystalline semiconductor island. 
     
     
       3. A device according to  claim 1 , wherein said thin film transistor is one selected from the group consisting of a stagger type and an inverted stagger type. 
     
     
       4. A device according to  claim 1 , wherein said liquid crystal material shows a cholesteric phase with no application of voltage. 
     
     
       5. A liquid crystal display device comprising: 
       a first substrate;  
       a second substrate opposing to the first substrate;  
       a light modulating layer being interposed between the first substrate and the second substrate, said light modulating layer including at least a liquid crystal material;  
       at least a pixel being formed over the first substrate, said pixel comprising:  
       a thin film transistor including a source region, a drain region, a channel region being interposed between the source and drain regions, a gate electrode being adjacent to the channel region with a gate insulating film interposed therebetween;  
       a drain electrode being connected to the drain region;  
       a gate line being connected to the gate electrode;  
       a common electrode being formed in parallel with the drain electrode;  
       a common line being connected to the common electrode,  
       wherein an electric field is formed between the drain electrode and the common electrode in a parallel direction to the first substrate,  
       wherein said light modulating layer is operated in a guest-host mode,  
       wherein said liquid crystal display device includes no polarizing plate,  
       wherein said liquid crystal material has a spiral pitch p in a range of 1≦p≦15 μm,  
       wherein a cell thickness d is in a range of 1≦d≦10 μm,  
       wherein molecules of said liquid crystal material have an orientation twist angle θ in a range of θ≦300°,  
       wherein an interelectrode distance L being defined between said drain electrode and said common electrode is in a range of L≦25 μm.  
     
     
       6. A device according to  claim 5 , wherein said light modulating layer further includes an optically active substance and a dichroic dye. 
     
     
       7. A device according to  claim 5 , wherein the source region, the drain region and the channel region are formed in a crystalline semiconductor island. 
     
     
       8. A device according to  claim 5 , wherein said thin film transistor is one selected from the group consisting of a stagger type and an inverted stagger type. 
     
     
       9. A device according to  claim 5 , wherein said liquid crystal material shows a cholesteric phase with no application of voltage. 
     
     
       10. A reflective type liquid crystal display device comprising: 
       a first substrate;  
       a second substrate opposing to the first substrate;  
       a reflection plate formed over one of said substrates;  
       a light modulating layer being interposed between the first substrate and the second substrate;  
       at least a pixel being formed over the first substrate, said pixel comprising:  
       a thin film transistor including a source region, a drain region, a channel region being interposed between the source and drain regions, a gate electrode being adjacent to the channel region with a gate insulating film interposed therebetween;  
       a drain electrode being connected to the drain region;  
       a gate line being connected to the gate electrode;  
       a common electrode being formed in parallel with the drain electrode;  
       a common line being connected to the common electrode,  
       wherein an electric field is formed between the drain electrode and the common electrode in a parallel direction to the first substrate,  
       wherein said light modulating layer is operated in a guest-host mode,  
       wherein said liquid crystal display device includes no polarizing plate,  
       wherein said light modulating layer comprises a liquid crystal material, an optically active substance and a dichroic dye,  
       wherein said liquid crystal material has a spiral pitch p in a range of 1≦p≦15 μm, and  
       wherein a cell thickness d is in a range of 1≦d≦10 μm.  
     
     
       11. A device according to  claim 10 , wherein the source region, the drain region and the channel region are formed in a crystalline semiconductor island. 
     
     
       12. A device according to  claim 10 , wherein said thin film transistor is one selected from the group consisting of a stagger type and an inverted stagger type. 
     
     
       13. A device according to  claim 10 , wherein said liquid crystal material shows a cholesteric phase with no application of voltage. 
     
     
       14. A liquid crystal display device comprising: 
       a first substrate;  
       a second substrate opposing to the first substrate;  
       a light modulating layer being interposed between the first substrate and the second substrate;  
       at least a pixel being formed over the first substrate, said pixel comprising:  
       a thin film transistor including a source region, a drain region, a channel region being interposed between the source and drain regions, a gate electrode being adjacent to the channel region with a gate insulating film interposed therebetween;  
       a drain electrode being connected to the drain region;  
       a gate line being connected to the gate electrode;  
       a common electrode being formed in parallel with the drain electrode;  
       a common line being connected to the common electrode,  
       wherein an electric field is formed between the drain electrode and the common electrode in a parallel direction to the first substrate,  
       wherein said light modulating layer is operated in a guest-host mode,  
       wherein said liquid crystal display device includes no polarizing plate,  
       wherein a light shielding means is formed over at least one of the first and second substrates to shield at least said channel region, and  
       wherein said light modulating layer comprises a liquid crystal material, an optically active substance and a dichroic dye,  
       wherein said liquid crystal material has a spiral pitch p in a range of 1≦p≦15 μm, and  
       wherein a cell thickness d is in a range of 1≦d≦10 μm.  
     
     
       15. A device according to  claim 14 , wherein the source region, the drain region and the channel region are formed in a crystalline semiconductor island. 
     
     
       16. A device according to  claim 14 , wherein said thin film transistor is one selected from the group consisting of a stagger type and an inverted stagger type. 
     
     
       17. A device according to  claim 14 , wherein said light shielding means comprises one selected from a metal and a polymeric material with a black pigment therein. 
     
     
       18. A device according to  claim 14 , wherein said liquid crystal material shows a cholesteric phase with no application of voltage. 
     
     
       19. A liquid crystal display device comprising: 
       a first substrate;  
       a second substrate opposing to the first substrate;  
       a light modulating layer being interposed between the first substrate and the second substrate;  
       at least a pixel being formed over the first substrate, said pixel comprising:  
       a thin film transistor including a source region, a drain region, a channel region being interposed between the source and drain regions, a gate electrode being adjacent to the channel region with a gate insulating film interposed therebetween;  
       a drain electrode being connected to the drain region;  
       a gate line being connected to the gate electrode;  
       a common electrode being formed in parallel with the drain electrode;  
       a common line being connected to the common electrode,  
       wherein an electric field is formed between the drain electrode and the common electrode in a parallel direction to the first substrate,  
       wherein said light modulating layer has first and second states, said first state being capable of transmitting a light while said second state being capable of absorbing the light,  
       wherein said light modulating layer comprises a liquid crystal material, an optically active substance and a dichroic dye, and  
       wherein said liquid crystal material has a spiral pitch p in a range of 1≦p≦15 μm.  
     
     
       20. A device according to  claim 19 , wherein the source region, the drain region and the channel region are formed in a crystalline semiconductor island. 
     
     
       21. A device according to  claim 19 , wherein said thin film transistor is one selected from the group consisting of a stagger type and an inverted stagger type. 
     
     
       22. A device according to  claim 19 , wherein said liquid crystal material shows a cholesteric phase with no application of voltage. 
     
     
       23. A liquid crystal display device comprising: 
       a first substrate;  
       a second substrate opposing to the first substrate;  
       a light modulating layer being interposed between the first substrate and the second substrate;  
       at least a thin film transistor including a source region, a drain region, a channel region being interposed between the source and drain regions, a gate electrode being adjacent to the channel region with a gate insulating film interposed therebetween;  
       a drain electrode being connected to the drain region;  
       a gate line being connected to the gate electrode;  
       an insulating film comprising an organic resin and being formed over the thin film transistor and the drain electrode;  
       a common electrode being formed in parallel with the drain electrode and being formed over the insulating film;  
       a common line being connected to the common electrode,  
       wherein an electric field is formed between the drain electrode and the common electrode in a parallel direction to the first substrate,  
       wherein said light modulating layer comprises a liquid crystal material, an optically active substance and a dichroic dye, and  
       wherein said liquid crystal material has a spiral pitch p in a range of 1≦p≦15 μm.  
     
     
       24. A device according to  claim 23 , wherein the source region, the drain region and the channel region are formed in a crystalline semiconductor island. 
     
     
       25. A device according to  claim 23 , wherein the thin film transistor is one selected from the group consisting of a stagger type and an inverted stagger type. 
     
     
       26. A device according to  claim 23 , wherein said liquid crystal material shows a cholesteric phase with no application of voltage. 
     
     
       27. A liquid crystal display device comprising: 
       a first substrate;  
       a second substrate opposing to the first substrate;  
       a light modulating layer being interposed between the first substrate and the second substrate;  
       at least a thin film transistor including a source region, a drain region, a channel region being interposed between the source and drain regions, a gate electrode being adjacent to the channel region with a gate insulating film interposed therebetween;  
       a gate line being connected to the gate electrode;  
       a first interlayer insulating film being formed over at least the gate electrode;  
       a drain electrode being connected to the drain region and being formed over the first interlayer insulating film;  
       a second interlayer insulating film comprising an organic resin and being formed over the first interlayer insulating film and the drain electrode;  
       a common electrode being formed In parallel with the drain electrode and being formed over the second interlayer insulating film;  
       a common line being connected to the common electrode,  
       wherein an electric field is formed between the drain electrode and the common electrode in a parallel direction to the first substrate,  
       wherein said light modulating layer comprises a liquid crystal material, an optically active substance and a dichroic dye, and  
       wherein said liquid crystal material has a spiral pitch p in a range of 1≦p≦15 μm.  
     
     
       28. A device according to  claim 27 , wherein the source region, the drain region and the channel region are formed in a crystalline semiconductor island. 
     
     
       29. A device according to  claim 27 , wherein the thin film transistor is one selected from the group consisting of a stagger type and an inverted stagger type. 
     
     
       30. A device according to  claim 27 , wherein said liquid crystal material shows a cholesteric phase with no application of voltage.